Abstract: Ant communities and their species diversity of the vertical band on east slope of the Gaoligongshan Mountains Nature Reserve are studied. The ant communities of the vertical band have obvious regularity on east slope of the nature reserve. Along with the altitude increasing, the number of dominant species of ant communities commonly decreases, but the percentage of dominant species increases. The quantity of species and individual density decrease with the altitude increasing. Along with altitude increasing, predominant index generally increases, but species diversity index and evenness index decrease. Some exceptions are also observed. The exceptional high predominant index and extraordinary low dominant species quantity, species diversity index and evenness index found in the Pinus yunnanensis forest at north section are related to the condition of the vegetation being a pure forest, however the extremely high species quantity and individual density of the forest are due to the marginal effect. The exceptional high predominant index and specially low dominant species quantity, individual density and species diversity index in the monsoon evergreen broadleaved forest at middle south section are caused by fragmentation of the vegetation. In contrast, the comparatively lower percentage of dominant species and predominant index, and the relatively higher species diversity index and evenness index in the upper portion of the mountain at middle north and middle south sections are related to the vegetation keeping a virgin forest state. Similarity coefficients between ant communities of the vertical band at all the 4 sections on east slope of the nature reserve are almost all in the range of 0～0.25 which representing an extremely dissimilar level. Only the similarity coefficient between ant communities of the Alnus nepalensis forest and monsoon evergreen broadleaved forest reaches the range of 0.25～0.50 which being a moderate dissimilar level.